Passive optical network (PON) system

Abstract

A PON system capable of utilizing the bandwidth of an optical transmission channel in the PON section. In a PON system including an OLT and a plurality of ONUs, the OLT has: a downstream frame processing unit that removes at least part of the header information in a layer 2 header from a downstream frame received from a wide area network, and converts the remaining frame portion into a frame having a header specific to the PON section; and a downstream frame processing unit that extracts a downstream frame portion to be transferred to a user terminal, from a received frame from a PON, and adds the layer 2 header information deleted in the OLT.

1. A passive optical network (PON) system including: a plurality of optical network units (ONUs) accommodating a user terminal, an optical line terminal (OLT) being connected to a wide area network and a passive optical network (PON) which connects between the ONUs and the OLT; the OLT transferring a downstream frame received from a communication node equipment in the wide area network to the plurality of ONUs via the PON; and the plurality of ONUs transferring the downstream frame to the user terminal,
 wherein the downstream frame includes a Layer 2 header and an IP packet, 
 wherein the OLT has a frame analyzing unit that judges whether a downstream frame received from the communication node equipment is a unicast frame or a multicast frame, outputs the downstream frame received from the communication node equipment without conversion when the downstream frame received from the communication node equipment is judged as a unicast frame and removes at least a part of the Layer 2 header information from the downstream frame received from the communication node equipment and outputs the downstream frame whose length is shortened when the downstream frame received from the communication node equipment is judged as a multicast frame; and a frame generating unit that generates a PON frame by adding a PON-specific header to the downstream frame outputted from the frame analyzing unit, and 
 wherein each of the ONUs has a downstream frame processing unit that extracts a downstream frame from the PON frame received via the PON, and adds a Layer 2 header information generated in said each GNU into the downstream frame when at least said part of the Layer 2 header information is removed. 
 
     
     
       2. The PON system of  claim 1 , wherein the downstream frame processing unit of said each ONU determines whether or not the PON frame to be processed in said each ONU for receiving the PON frame is included based on the identification information in the PON-specific header of the PON frame received from the OLT, and discards the PON frame when the PON frame does not include the frame to be processed in said each ONU for receiving the PON frame. 
     
     
       3. The PON system of  claim 1 , wherein the downstream frame processing unit of said each ONU determines whether or not the PON frame contains a multicast IP packet based on the identification information in the PON-specific header of the PON frame received from the OLT, and when it is determined the PON frame contains a multicast IP packet, adds Layer 2 header information generated in said each ONU. 
     
     
       4. The PON system of  claim 1 , wherein said each ONU holds the address of the participant user terminal for each multicast group, and
 wherein the downstream frame processing unit of said each ONU determines whether or not the PON frame contains a multicast IP packet based on the identification information in the PON-specific header of the PON frame received from the OLT, and when it is determined the PON frame contains a multicast IP packet, refers to the destination IP address of the multicast IP packet and the address of the participant user terminal held for each multicast group, and when a participant user terminal is not registered in a multicast group identified by the destination IP address, discards the PON frame. 
 
     
     
       5. The PON system of  claim 4 , wherein said each ONU transfers the downstream frame judged that the downstream frame contains the multicast IP packet to a line to which a participant user terminal of the multicast group of identified by the destination IP address of the multicast IP packet is connected. 
     
     
       6. The PON system of  claim 1 , wherein a downstream frame which the OLT received from the communication node equipment contains an Ethernet header as a Layer 2 header. 
     
     
       7. The PON system of  claim 1 ,
 wherein a downstream frame which the OLT received from the communication node equipment contains an Ethernet header as a Layer 2 header, and 
 wherein the frame analyzing unit of the OLT removes at least a destination MAC address, a source MAC address, and a protocol type from a downstream frame in the information of the Layer 2 header of the downstream frame, and 
 the downstream frame processing unit of said each ONU adds at least a destination MAC address, a source MAC address, and a protocol type generated therein as the Layer 2 header information to the downstream frame extracted from the PON frame received from the OLT via the PON. 
 
     
     
       8. The PON system of  claim 1 , wherein the frame analyzing unit of the OLT judges whether the downstream frame is a multicast frame or a unicast frame based on a destination address included in the Layer 2 header of the downstream frame received from the communication node equipment. 
     
     
       9. The PON system of  claim 1 , wherein the frame generating unit of the OLT generates the PON frame by adding a PON-specific header including a multicast port ID to the downstream frame outputted from the frame analyzing unit, when the downstream frame received from the communication node equipment is judged as a multicast frame.